The problem of coating and of covering supports that have not been pretreated and are often wet, rises particularly in respect to bituminous emulsions which must adhesively coat granular and filamentary compositions, taken as they come, on their deposits in the open.
It is a fact that wet materials do not accept in this condition coating with hydrocarbons. The water being in effect the principal occupant, it has until now been necessary either to dry the materials or to displace the water chemically.
A first solution satisfying these problems has been proposed by French patent application 2686811 and European patent application 0 555 167, useful both for hot coating and for cold coating.
The process described in these applications comprises rendering hydrophobic the supports to be coated, by cold pretreatment, by causing to react, in contact with these supports, two hydrophobic vectors, namely: a metallic salt and a fatty acid or similar products. When these latter are mixed with dry or low humidity supports, the hydrophobic nature appears spontaneously, without drying. Moistened with more than 1% water, the support materials, particularly the filamentary ones, must be dried after having added and mixed the hydrophobic vectors, which is also the case for the open granulometry materials. This drying must be carried out cold, hence without the use of a drying drum.
The mineral granulates thus pretreated can be adhesively coated with any bituminous binder, no matter what its form.